RU2766130C1 - Method for diagnostics of bearings of rotary equipment based on the assessment of microvariations of rotation of the shaft - Google Patents

Abstract

FIELD: testing.

SUBSTANCE: invention relates to the field of non-destructive testing and can be used for diagnostics of the condition of bearings of rotary equipment, e.g., reducer gearboxes, turbines, engines, and generators. Claimed is a method for diagnostics of bearings of rotary equipment based on recording microvariations of rotation of the shaft by installing a rotation speed sensor (RSS) on the shaft of the tested article, generating pulses of a standard form at times t_i at the values of the shaft angle φ=(360/N)i, wherein N is the number of pulses in a full revolution of the shaft, i=1, 2, 3, … is the number of the pulse, obtaining a sequence of inter-pulse intervals {T_i}, wherein T_i=t_i+1-t_i, assessing the variability T_i by finding the root mean square deviation σ of values of T_i from the mean value

. The sequence {T_i} is therein filtered, the root mean square deviation σ of the values of

from the average value of

is found for the filtered sequence

, and if the recorded σ is higher than the determined value, then a conclusion is made about the presence of a bearing defect in the tested article.

EFFECT: increase in the sensitivity of diagnostics.

1 cl, 2 dwg

Description

The invention relates to the field of non-destructive testing and can be used to diagnose the condition of the bearings of rotary equipment, examples of which are gearboxes, turbines, engines and generators.

Non-destructive diagnostics for such products is usually performed on the basis of registration and subsequent analysis of signals received from a vibroacoustic sensor or from a shaft speed sensor (RSV) installed on the controlled equipment. As a result of the analysis of the recorded signals, informative signs of defects are revealed, which make it possible to judge the state of the product under study.

The closest technical solution to the proposed method is a method based on estimating the variability of the interpulse intervals of the pulse sequence obtained from the DChV (Kolokolov A.S., Lyubinsky I.A. Method for diagnosing mechanisms, assemblies and machines based on the assessment of microvariations of shaft rotation: Patent for Invention No. 2626388 RF; Registered 07/26/2017).

To implement this method, a DChV is installed on the shaft of the controlled product, which generates pulses during the rotation of the shaft at angle values ϕ=(360/N)i, where N is an integer that determines the number of pulses per shaft revolution, i=1, 2, 3, ... - pulse number, in the pulse sequence generated by the DHF, the measurement of the time intervals between the pulses of the sequence is performed. Based on the measurement results, the root-mean-square deviation of the inter-pulse intervals from the average value is found and, if the obtained value of σ is above a certain threshold, then a conclusion is made about the presence of a defect in the controlled product. Thus, the value of σ is an informative sign of the presence of a defect. The disadvantage of this method is its very low sensitivity. Since for serviceable and defective bearings the relative change in the value of σ is about 1.8.

The technical result of the invention is to increase the sensitivity of the method discussed above in relation to the problem of diagnosing bearings by filtering the sequence of interpulse intervals in the pulse sequence recorded with DFC, and subsequent estimation of the informative parameter σ for the filtered sequence. The purpose of filtering is to amplify in the resulting sequence of interpulse intervals of high-frequency microvariations associated with defects in bearings and attenuate microvariations created by other elements of rotary equipment, for example, a rotor, which, with the development of its imbalance, generates relatively low-frequency variations in interpulse intervals.

; отличающийся тем, что с целью повышения чувствительности диагностики производят фильтрацию последовательности p(i)={T_i), для отфильтрованной последовательности

находят среднеквадратичное отклонение σ значений

от среднего значения

и, если зафиксированное σ выше определенной величины, то делают заключение о наличии дефекта подшипников у контролируемого изделия.The technical result is ensured by the installation of a controlled product on the shaft of the DChV, which generates standard-shaped pulses at the moments of time t _t at the values of the shaft angle ϕ=(360/N)i, where N is the number of pulses per full revolution of the shaft, i=1, 2, 3 ... . - pulse number, obtaining a sequence of interpulse intervals {T _i }, where T _i =t _i+1 -t _i , assessing the variability of T _i by finding the standard deviation σ of the values of T _i from the average value

; characterized in that, in order to increase the sensitivity of diagnostics, the sequence p(i)={T _i ) is filtered, for the filtered sequence

find the standard deviation σ of the values

from the average

and, if the fixed σ is higher than a certain value, then a conclusion is made about the presence of a defect in the bearings of the controlled product.

In FIG. Figure 1 shows a block diagram explaining the process of evaluating microvariations of shaft rotation.

1 - shaft DFC, 2 - block for estimating the moments of occurrence of pulses generated by DFC, 3 - block for constructing a sequence of interpulse intervals, 4 - digital filter with a finite impulse response, 5 - block for filtering a sequence of intervals, 6 - block for estimating the average interpulse interval and standard deviation interpulse interval a from the average value.

In FIG. 2 shows four graphs representing variations relative to the average value of the interpulse intervals in the original and filtered sequences p(i) and p _f (i), for serviceable and defective bearings.

1 and 2 - interval variations in the initial sequences of interpulse intervals p(i) for serviceable and defective bearings, 3 and 4 - interval variations in the filtered sequences of interpulse intervals p _f (i) for serviceable and defective bearings.

The technical result is achieved by performing the following sequence of operations for processing the signal s(t) with DFA.

1. Time points t _i (i=0, 1, 2, …) of intersection s(t) of threshold level θ ₀ are found at ds/dt>0. The result is a sequence p ₀ (i)={t _i }. In the case of a digitized signal s(kΔt), where k=0, 1, 2, …, Δt is the sampling interval, linear interpolation s(kΔt) should be used to ensure the accuracy of t _i estimation.

2. Based on the sequence p ₀ (i) measure the interpulse intervals T _i =t _i+1 -t _i and form a sequence of interpulse intervals p(i)={T _i }.

3. The sequence p(i) is digitally filtered by a filter with a finite impulse response h(m), where m=0, 1, 2, …. The purpose of filtering is to identify in the resulting sequence p(i) inter-pulse intervals of relatively high-frequency microvariations associated with defects in bearings, and attenuation of low-frequency microvariations generated by other elements of rotary equipment, for example, a rotor during the development of its imbalance. Fig. 2 explains the filtering results. On it, graphs 1 and 2 represent the interval variations in the initial sequences of interpulse intervals p(i) for serviceable and defective bearings, and 3 and 4 - interval variations in the filtered sequences of interpulse intervals p _f (i) for serviceable and defective bearings.

и среднеквадратичное отклонение σ ее интервалов

от среднего значения

.4. For the filtered sequence p _f (i) determine the average interpulse interval

and standard deviation σ of its intervals

from the average

.

5. When σ values exceed a certain value, a conclusion is made about the presence of a defect in the bearing.

Application of the proposed method to the real task of diagnosing roller bearings on a bench when registering s(t) using a 16-bit ADC with a sampling rate of 50 kHz, using an inductive DFA with N=24 and a three-point high-pass filter with an impulse response h(1) as an example =-0.25, h(2)=0.5, h(3)=-0.25 confirmed its effectiveness. It was found that when using filtering, the value of σ for bearings with defects was approximately 4.2 times greater than for serviceable bearings, which indicates a more than twofold increase in the sensitivity of the proposed method compared to its prototype.

Thus, the above data allow us to conclude that the proposed method can be used to improve the quality of diagnostics of bearings of rotary equipment, as well as to monitor the development of a defect.

Claims (1)

A method for diagnosing bearings of rotary equipment based on registering microvariations of shaft rotation by installing a speed sensor (RPS) on the shaft of the controlled product, which generates standard-shaped pulses at time t _i at values of the shaft angle ϕ=(360/N)i, where N is the number of pulses on a full revolution of the shaft, i=1, 2, 3, … - pulse number, obtaining a sequence of interpulse intervals {T _i }, where T _i =t _i+1 -t _i estimating the variability of T _i by finding the standard deviation σ values T _i from the average value

; characterized in that, in order to increase the sensitivity of diagnostics, the sequence {T _i } is filtered, for the filtered sequence

find the standard deviation σ of the values

from the average

and, if the fixed σ is higher than a certain value, then a conclusion is made about the presence of a defect in the bearings of the controlled product.

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